I've been playing around with focus stacking lately and that has led me to exposure stacking, which is the technique used here. I'm wondering what you think about the result? Is it worth the effort? I mean, it's not difficult, but if it doesn't add to the result, why bother?

I'm using a D7000 with a 105 f/2.8 Manual Focus lens set at F22, from about 6 feet away. Natural light through a large window with a diffusion drape between the source and the subject, and a boom mounted reflector opposite for fill light.

I processed this in Photoshop 5, opening all three shots as separate layers, then aligned and blended them, before merging the layers into one. I then did a layers adjustment, a shadows and highlights adjustment, USM @ 150/1.2/2 then cropped to 8 x 10 ratio. I also did some minor noise reduction in LR3. Lastly, I added a square black vignette with the center pulled to the edges to burn off the stems as they exit the frame.

The results are quite nice but in a controlled lighting situation where a fill source is used you should be able to record a full range of detail on the sensor without needing to resort to multiple exposures.

It's trivial with flash: Just start with neutral centered fill and raise it's power until the desired shadow detail is seen, then turn on and overlap the key and accent lights and raise power until they are below clipping in all but the specular highlights.

Where exposure stacking is need is cross-lit outdoor scenics which always exceed the sensor's range.

cgardner wrote:
I realize flash wasn't used, what I was suggesting was that using flash would be a simpler means to arrive at same results— a full tonal range.

FWIW — the final results don't look like a window lit shot of a flower. It looks more like a flower lit with flash. That being the case actually using flash would be simpler.

You did after all ask, "Why bother?" did you not?

Thanks for the comments. I appreciate the feedback. Although, from my perspective, using flash is far less simpler since I would have to set up more equipment, meter everything, add diffusion to each flash, etc. And I'm actually quite pleased with the result, since to me it has effective dynamic range and depth. I did ask, so not arguing with you, just stating my thoughts....!

AuntiPode wrote:
Sorry if I'm not more helpful, but I've been battling a cold for several days and I'm sub-parr.

"Down - Under" ??

Curious @ focus stacking w/ f22. It seems like the effort of focus stacking is being lost a bit on the amount of diffraction (contrast reducing) that is generated by being stopped down that far. In this case, it looks like you've got some good strong (south or west facing) direct window light sufficient to help offset the diffraction, but if you were using 'softer' light the reduction in contrast @ diffraction would likely be more noticeable.

Since you are focus stacking, why not use a less diffraction inducing aperture, i.e. f11-f13 vs. f22? I realize that this will reduce the DOF a bit for each snap, and may require an additional image to be captured, but I wouldn't get too fond of f22 ... unless you have strong direct light. Just something for future consideration.

Curious @ focus stacking w/ f22. It seems like the effort of focus stacking is being lost a bit on the amount of diffraction (contrast reducing) that is generated by being stopped down that far. In this case, it looks like you've got some good strong (south or west facing) direct window light sufficient to help offset the diffraction, but if you were using 'softer' light the reduction in contrast @ diffraction would likely be more noticeable.

Since you are focus stacking, why not use a less diffraction inducing aperture, i.e. f11-f13 vs. f22? I realize that this will reduce the DOF a bit for each snap, and may require an additional image to be captured, but I wouldn't get too fond of f22 ... unless you have strong direct light. Just something for future consideration.

thanks Kent. I didn't change the focus on these. I only changed the shutter speed to allow for three different exposures, then combines them via Photoshop. I really have no idea what you mean by diffraction. In these shots, I had direct light that was diffused. Is that what you mean by diffraction? all three posts are a combination of three shots at different shutter speeds.

Okay. so I looked up the definition of diffraction and it generally means a loss of sharpness at small apertures. So in the third shot, at F/11, I can't find any loss of sharpness. Could you please point it out? I'm totally at a loss to see what is meant by this!

In this case, diffraction *might* degrade the sharpness slightly, but I suspect a more visible effect might be a reduction in micro contrast. If you don't stack, then using a small aperture can be a good choice. If you overlap the DOF by stacking images with different planes of sharpest focus, you can have the image quality of the optimum aperture combined with the depth of field that ordinarily requires a small aperture. For a subject like this, the small potential improvement might be detectable. That's why I suggested trials with the lens at it's optically best aperture.

Okay got it. So, in this case, since neither the focus nor the aperture changed, does that still apply? Like i said, the only thing that changed for each of the three shots that were combined to create each of three images above, was shutter speed. So in my thick head, the only thing that changed was the amount of light reaching the sensor, while the DoF and focal depth remained static.

I guess starting the thread with "I've been playing around with focus stacking" is lending to some confusion since its not the technique used on these shots. It's just what lead me to "exposure stacking."

Gotcha @ 'exposure stacking' vs. focus stacking on this one. I got a bit hyper-focused on the focus stacking part.

That being said though, I think your f22 vs. your f11 posts here depict the kind of difference that diffraction causes. While it may mildly degrade sharpness, it also degrades contrast (highly inter-related). This can be somewhat offset or amplified when combined with high vs. low contrast lighting. Also, it does depend somewhat on your lens resolving capabilties and sensor pixel size as to whether or not it's effects are being realized.

I realize that we don't know how much variation there is between your three images via PP, but on the premise that they were processed somewhat similarly, the contrast difference between your f22 vs. the two @ f11 seems in line with the aperture change. It's not a glaring diff @ stand alone, but in comparison, it becomes more notable.

It's not that it is necessarily "taboo" or that diffraction will "ruin" your shots ... BUT, if you are going to the level of effort involved with "stacking" to achieve optimal results ... letting diffraction stay in the picture kinda defeats the purpose for the exceptional effort (imo) intended to generate exceptional results.

As Karen has noted in the past ... if you need the DOF of a "diffraction producing" aperture, your need for DOF trumps diffraction. But, if one is going to be stacking, or the DOF difference isn't critical ... I typically open up to f11 or f13 for my "Max DOF" ... reserving beyond f16 mostly to generate longer shutter speeds for motion blur (where diffraction doesn't matter much anyway).

For general purpose and with sufficiently strong lighting, the effects of diffraction aren't realized by most people ... but I reason that you are striving for exceptional vs. general purpose.

Here's a link that I find helpful for both understanding diffraction ... and a couple of interactive tools to help you see the differences involved at various apertures vs. pixel dimension.

Thanks for that explanation and link Kent. That was very helpful and much easier for me to understand! I'm finding that very few of the images I admire most are simple one click shots and that much more technique is involved with producing exceptional images. Landscape shots in particular are a combination of several shots, merged and blended by masters of post processing, but the common attribute they all share is they don't look like there was a lot of PP involved. So understanding diffraction is a good thing for me in that if the sharp eye sees it, then so should I!

So if I understand this better, using the larger aperture in the last shot helped reduce diffraction because less of the light reaching the sensor was altered from its original path in reaching the sensor. Its almost counter intuitive for me in the floral portrait shots that I do, because when I started, one of the first lessons I learned was smaller aperture means greater DoF. While that still holds true to an extent, adding multiple layers at a larger aperture now seem beneficial in order to effect the least amount of light change. Now I just need to recognize it!

Admitting I have not done a thorough read, does the f/11- diffraction behavior apply to lenses not designed for digital? I interpreted Greg's as a non-digital, manual focus Nikkor, one of which I gave to my daughter several years ago.

Bob Jarman wrote:
Admitting I have not done a thorough read, does the f/11- diffraction behavior apply to lenses not designed for digital? I interpreted Greg's as a non-digital, manual focus Nikkor, one of which I gave to my daughter several years ago.

Bob

That's a good question Bob! I would guess that the quality of the glass also plays a part on how the light is resolved, in addition to how much the light is "squeezed" though the diaphragm.. But in defense of the Nikkor AiS lens I used, I find it resolves better than much of the AF glass in my kit! I have three of the AiS lenses and being perfectly honest, I would use none of them handheld, as I just don't have the skill to hold still long enough to get them focused properly, but on a tripod, I believe the results are hard to beat unless you move into the Leica realm.....